Make sure the cranberry juice is very cold. Pour the sljivovica into the glass/jar/whatever first, then the juice afterwards. No ice. Works best, of course, with a good, very strong homemade sljivovica, but lacking that, store-bought sljivovica/plum brandy works too. Also make note that this is NOT a sweet plum liqueur type of thing but a very dry, usually very strong distillate of plums.